Washington D.C.- A brief argument between Vice President Cheney and a senior Democratic senator led Cheney to utter a big-time obscenity on the Senate floor this week.

On Tuesday, Cheney, serving in his role as president of the Senate, appeared in the chamber for a photo session. A chance meeting with Sen. Patrick J. Leahy (Vt.), the ranking Democrat on the Judiciary Committee, became an argument about Cheney’s ties to Halliburton Co., an international energy services corporation, and President Bush’s judicial nominees. The exchange ended when Cheney offered some crass advice.

“Fuck yourself,” said the man who is a heartbeat from the presidency.

Leahy’s spokesman, David Carle, yesterday confirmed the brief but fierce exchange. “The vice president seemed to be taking personally the criticism that Senator Leahy and others have leveled against Halliburton’s sole-source contracts in Iraq,” Carle said.

As it happens, the exchange occurred on the same day the Senate passed legislation described as the “Defense of Decency Act” by 99 to 1.

Cheney’s office did not deny that the phrase was uttered. His spokesman, Kevin S. Kellems, would say only that this language is not typical of the vice presidential vocabulary. “Reserving the right to revise and extend my remarks, that doesn’t sound like language the vice president would use,” Kellems said, “but there was a frank exchange of views.”

Gleeful Democrats pointed out that the White House has not always been so forgiving of obscenity. In December, Democratic presidential candidate John F. Kerry was quoted using the same word in describing Bush’s Iraq policy as botched. The president’s chief of staff reacted with indignation.

“That’s beneath John Kerry,” Chief of Staff Andrew H. Card Jr. said. “I’m very disappointed that he would use that kind of language. I’m hoping that he’s apologizing at least to himself, because that’s not the John Kerry that I know.”

This was not the first foray into French by Cheney and his boss. During the 2000 campaign, Bush pointed out a New York Times reporter to Cheney and said, without knowing the microphone was picking it up, “major-league [expletive].” Cheney’s response — “Big Time” — has become his official presidential nickname.

Then there was that famous Talk magazine interview of Bush by Tucker Carlson in 1999, in which the future president repeatedly used the F-word.

Tuesday’s exchange began when Leahy crossed the aisle at the photo session and joked to Cheney about being on the Republican side, according to Carle. Then Cheney, according to Carle, “lashed into” Leahy for remarks he made Monday criticizing Iraq contracts won without competitive bidding by Halliburton, Cheney’s former employer.

Leahy, Carle said, retorted that Democrats “have not appreciated White House collusion in smears” that Democrats were anti-Catholic for blocking judicial nominees such as William H. Pryor Jr. Democrats demanded that Bush disavow the allegations by conservative groups, but the White House did not.

The Democratic National Committee has declared this to be “Halliburton Week” to portray administration ties to the controversial company. “Sounds like it’s making somebody a little testy,” Kerry spokesman Chad Clanton said.

Republicans did their best to defend the vice president. Senate Judiciary Committee Chairman Orrin G. Hatch (R-Utah), while pointing out that he was unaware of the incident, described Cheney as “very honest” and said: “I don’t blame anyone for standing up for his integrity.”

There is no rule against obscene language by a vice president on the Senate floor. The senators were present for a group picture and not in session, so Rule 19 of the Senate rules — which prohibits vulgar statements “unbecoming a senator” — does not apply, according to a Senate official. Even if the Senate were in session, the vice president, though constitutionally the president of the Senate, is an executive branch official and therefore free to use whatever language he likes.